1. Field of the Invention
The present invention relates to an internal combustion engine having a variable valve operating device.
2. Description of Background Art
An internal combustion engine which is mounted on a vehicle is known wherein a valve operating mechanism is provided on a cylinder head with a valve characteristic variable mechanism for controlling the respective operational timings and maximum lift quantities of an intake valve and an exhaust valve. See, for example, JP-A-2005-207254, JP-A-2005-207255, JP-A-2004-27865, JP-A-2002-70596 and JP-A-2000-291419.
The valve characteristic variable mechanism includes a single actuator, an electrically operated motor, a hydraulic cylinder or the like, as a drive source corresponding to the intake and exhaust valves. Since the actuator becomes bulky or takes a relatively large space, the actuator is usually arranged outside a valve operating chamber separately from respective parts of the mechanism.
In the above-mentioned internal combustion engine, to efficiently make use of an EGR (Exhaust Gas Recirculation) combustion range having a favorable fuel economy by properly setting a valve overlap quantity or the like in response to an operational state (under a loaded state), it is desirable to individually control intake and exhaust sides of a valve operating device. However, in such a case, it is necessary to sufficiently study a layout of the actuator which is liable to take a large space.